RE: suspension

["Dave Eaton" <Dave.Eaton@clear.net.nz>]

thanks for the information.  i think that we're in danger of a rat hole
here.  if you re-read my original note i stated that one of the major points
of differentiation for a suspension designer between wishbones and struts
was the likelyhood of having to cater for major suspension movement.  when
this is likely, struts are preferred.  hence the use of struts in rally
cars.  front and rear.  so clearly i disagree that a wishbone will
out-preform a strut in this respect (particularly over high degrees of
travel). no question that wishbones are the choice for circuit cars.  or
that they are a better "theoritical" choice in low-wheel-movement cases -
their limitations wrt packaging noted.  can wishbones work in high wheel
travel situations?  certainly.  but the guru's clearly think that struts are
the best compromise for the rough stuff.  and most also that wishbones are
not good enough at the rear for many street (comfort rather than outright
performance) applications...

interestingly the recent "race car engineering" magazine has an article
about the ford focus rally car, looking at design and engineering issues.
very nice pictures of the front struts.  ditto a recent autocar article.
the autocar article has more information about gunter steiner's (project
leader) decision to go with struts front and rear rather than the oem
wishbone rear suspension, and the reasons why (basically better ability to
handle 10-12" of wheel movement). the old escort rally car had struts front
and rear also.

hth,
dave
'95 rs2
'90 ur-q
'61 mb fintail
-----Original Message-----
From: Darren Wall [mailto:dwall@sisna.com]
Sent: Friday, 11 June 1999 10:34
To: Dave.Eaton@clear.net.nz; quattro@audifans.com
Subject: RE: suspension

I disagree with you about the advantage of a strut type suspension over a
wishbone type suspension.  The main function of a suspension is to keep the
tire contact patch as consistent as possible while allowing the tire to
follow the profile of the road.  A well designed double wishbone suspension
will allow less tire camber change through a greater range of up-down motion
than a strut type suspension.  The advantages of strut type suspensions, and
the reason they are so prevelant on modern cars is:  1) They are cheap to
produce.  The component count is low and they are mostly off-the-shelf
items.  2) They are relatively compact.  The strut takes a fair amount of
space vertically, above the tire, but they leave a lot of space between the
front tires, ideal for front wheel drive cars.  3) They are fairly
lightweight.  A-arm suspensions can be made as light as strut type
suspension, but they require more exotic materials, which drives the cost up
even farther.

[snip]